Generally, an electric storage apparatus includes an electric storage device 1 that includes an external terminal 4, and a bus bar 6 that is connected electrically to the external terminal 4, as shown in FIG. 12. In some electric storage apparatuses of this type, the external terminal 4 of the electric storage device (battery cell) 1 and the bus bar 6 are connected to each other by welding.
In such an electric storage apparatus, the external terminal 4 has a flat first connection surface 4a. Meanwhile, the bus bar 6 has a flat second connection surface 6a which overlaps the first connection surface 4a. The external terminal 4 and the bus bar 6 are welded together in a state where the first connection surface 4a and the second connection surface 6a overlap each other. That is, a weld portion 9 in which the external terminal 4 and the bus bar 6 are partially melted and fused is formed in a region where the first connection surface 4a and the second connection surface 6a are opposed to each other. This allows the electric storage device 1 and the bus bar 6 to be conductively connected to each other (for example, see JP 2012-125829 A).
In the aforementioned electric storage device 1, the weld portion 9 is formed. Following this, there are cases where hollow blowholes B occur in the periphery of the weld portion 9. When the blowholes B occur, the width of the junction between the external terminal 4 and the bus bar 6 is narrowed. Therefore, the strength of the weld portion 9 is reduced as compared to the case where no blowholes B occur.
Further, for example, when the electric storage device 1 or the bus bar 6 vibrates, or the bus bar 6 is bent for position adjustment, stress is concentrated in the periphery of the weld portion 9. In such a case, the stress concentrated in the periphery of the weld portion 9 may possibly cause damage in part of the weld portion 9 when the weld strength is reduced due to the influence of the blowholes B. Therefore, there is a possibility of failure to ensure the stiffness of the connection between the external terminal 4 and the bus bar 6.